Glad you liked it, BT.
The article came from a paperback, The Presidential Papers, in which Mailer purported to give advice to the new President, JFK, in the form of a series of essays. I never thought of Mailer as a Gonzo journalist, but I could see the resemblance as soon as I read your post. The Wikipedia article on Gonzo Journalism didn't include Mailer, but it linked to the "New Journalism," an earlier trend, and included Mailer as part of the New Journalism school, along with some other writers who are clearly Gonzo. So I guess it's a pretty subjective categorization with fairly fluid boundaries.